controlling humidity

QuentinQuark said:

Hey all,

Trying to design a sealed room.

Cool-tubed lights to control expel thermal heat coming from HIDs.

CO2 tank to bring fresh CO2 without generating heat.

Carbon scrubber to get rid of odour.

And I thought I had the temperature problem solved by going with a dual-hose A/C (with heating) that didn't "bleed" room air out the exhaust hose. This would let me heat or cool as needed, without losing CO2.

Then I got to thinking about humidity. And about the fact that with a portable A/C, I have no control over my humidity. The thing will drain as much moisture out of the air as it can. If I want it more humid that ambient humidity, I have no way of doing that. If I want it less humid than ambient humidity, well I can cross my fingers and hope the A/C does it's thing.

So then I got to thinking that maybe I could use a swamp cooler instead of an A/C, that would let me up the humidity if I wanted to. But that still doesn't give me direct control over the humidity, in fact it basically gives me the opposite problem as the A/C, it humidifies at will, whereas the A/C dehumidifies at will.

The trouble with an A/C or a swamp cooler is that they affect humidity as a side effect of temperature control - they don't give you direct control over humidity itself.

So I'm thinking the only way to get actual control over humidity would be to put in a humidifier and a dehumidifier.

Now I know some people are gonna be like "why would you want MORE humidity, you'll get mold, powdery mildew, etc!". My A/C does too good of a job dehumidifying, it's like 30% and that's too dry. They actually do better around 55%, and I would like to experiment around 75%. I have a sulfur burner so I'm not concerned about mold/PM.

So is a humidifier and a dehumidifer my only choice if I want to control humidity? Is anyone doing this?

Thanks!

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Treeth said:

Hey quentin,

I hear you on the issue of keeping the stomata dilated in the face of 1500 ppm and what sort of results that will bring,

Reading today on the thread "increasing thc" - or something like that,

a low rh was pointed to as incresing trichome glands as a response to protecting what-will-be-kept sensimilla from the hostile outside environment.

So outside of veg, low rh is good. my indoor ac keeps thing at 30%, and i never have to drain it as all the water gets expelled by the very hot exhaust.

Thinking about it now, wouldn't a low rh increase transpiration, and therefor osmosis in the roots, increasing the amount of water and nutrients coursing through the plant, regardless of how effective the respiration is in the leaf material?

And- of the plant wants more respiration, it'll grow larger fan leaves, would it not? This is only my own musing...

I also think that, ideally, or at least the goal here of efficacious growing, is to keep the vegitative material to a minimum. The more plant material you have the more energy is expended in its interest... Certainly a good amount is needed for abundant sensimilla but still,

we want a combination of optimum growing conditions, in a dichomoty with reproductive stress.

Reaching this place is open to much experimentation... I think smallish fan leaves are the best indicator of this, or a high bud to leaf ratio by mass... something like that would be a very insightful way to analyze efficacy...

Add a umm ultrasonic humidifier if you are concerned or want to experiment, nicer units will have built in cut offs for a user selectable rh, unless you have a nice environmental logic box.

I wouldn't worry about humidity.

its you're last concern anyways, far after light and feeding, which affect growth way more than feeding. And after optimum conditions for growth are aqcuired, you must induce stress in playing with those enviromental variables , again. I think a low rh is given to you by the ac, so just take it.

I really only think i've seen dehumidifiers in grows before. never re-humidifiers. I suppose for set ups like that, at a point, running the de h is pointless, especially below 40-50% ill bet as the additional safety from mold and easy stress is offset by the additional heat put out by the unit, which has to be fought by the ac.

Not that many people have sealed rooms as we do. The people who look into this kind of control have large grows and large budgets, and are often working with central air-

These indoor units are pretty rare in our application, actually, i have a couple ultrasonics from when i was trying to use them for an aero grow, i'll throw wat i got in my room and test it out... though I doubt i'll see any difference.

Open stomata for increased respiration, when the plant is choking on water saturated air... when it can't get rid of its water from respiration because the rh is too high...

Thats what I think. I do associate giant amount of foliage with high rh though as in jungles... but still... if they could they wouldn't need all that surface area to get the job done.

My advice... promote such growth in veg, and not be concerned about it in flower.

peace! lol

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